Thanos's adopted daughter, and the one member of his order who fights like she wants to be there.
Proxima Midnight is Thanos’s adopted daughter, voiced and faced by Carrie Coon and motion captured by Monique Ganderton. She joins his search for the Infinity Stones and takes part in the attack on the Statesman, helping kill the Asgardians aboard to get the Space Stone. With Corvus Glaive she attacks Wanda Maximoff and Vision for the Mind Stone, and Steve Rogers, Natasha Romanoff and Sam Wilson drive them off.
She is a useful reminder that Gamora and Nebula are not the only adopted children in that family, and that the others made a different choice about it.